A 1980s motorboat spray-painted submarine yellow carved a straight line across a calm White Bear Lake one recent morning. Then it turned and methodically crossed again, and again, as if mowing a giant lawn.
Aboard the vessel, Christopher Olson steered while Ann Merriman trained her eyes on a sonar scan of the lake’s bottom. The couple, underwater archaeologists and co-founders of Maritime Heritage Minnesota, hoped to discover some history.
It’s a labor of love for the St. Paul pair, who between the two, have studied underwater archaeology in Greece, examined a wrecked Civil War-era boat off the coast of the Carolinas and dove on the USS Arizona at Pearl Harbor.
Minnesota lakes tell stories, too, they say. They are working to document — but not disturb — their submerged findings for the state’s archaeological records.
“It’s everyday stuff that rarely gets recorded,” Olson said. “It falls through the cracks of history.”
When something interesting appears on the screen — sometimes dozens of times on a given lake — they document its GPS coordinates in a notebook to come back for further inspection. If it still looks interesting, they might do a dive, with the help of their volunteers, for a better look.
In nearly 20 years, the couple’s nonprofit has documented more than a dozen Minnesota bodies of water, including Lake Minnetonka, Christmas Lake and Lake Waconia, as well as parts of the Mississippi and Minnesota rivers and a wreck on Lake Superior.

Now, some wrecks are under threat from blasts of boat prop wash — especially with the popularity of wake surfing, which creates an especially powerful force. Scanning water bodies for archaeological purposes requires permits, and taking anything from archaeological sites is illegal, but some divers do it anyway, Merriman said.